Stream level uninterrupted restore operation using data probe

ABSTRACT

Methods and systems for restoring data from a target device are described. According to some embodiments, the method receives a first set of data packets for restore, where the first set of data packets includes a multiplicity of data chunks. The method further captures footprints of the first set of data packets in a cache disk array. In response to receiving an acknowledgement from the cache disk array indicating the footprints of the first set of data packets have been captured, the method pushes each data chunk of the first set of data packets to a construction container for reconstruction of backup data. In response to receiving an acknowledgement from the construction container indicating the data chunk is successfully pushed, the method flushes the respective footprint of the data chunk from the cache disk array.

RELATED APPLICATIONS

This application is related to co-pending U.S. patent application Ser.No. ______, entitled “Stream Level Uninterrupted Backup Operation UsingData Probe,” filed Jun. 26, 2019, Atty. Docket No. 206368.0516.9 (P330),the disclosure of which is incorporated by reference herein in itsentirety.

FIELD OF THE INVENTION

Embodiments of the present invention relate generally to data storagesystems. More particularly, embodiments of the invention relate tostream level uninterrupted backup operation using a data probe approach.

BACKGROUND

Unexpected events can cause backup and/or restore operations to abortprior to the completion of such operations. The need to start successivebackups (or restores) from the point of interruption to avoid anincrease in backup or restore window has become vital nowadays. Whilethe backup or restore operation is in progress and due to some randomunintended event, the operation would abruptly abort, thereby causingdata to be partially written (e.g., half written) back to the targetdevice or host. Also, the backup or restore would be rolled back afterthis point in most of the cases resulting in unusable data andpotentially corrupted production environment. Such situation would leadto an increase of backup or restore window. Additionally, other painpoint is that the backup or restore must be restarted again from thebeginning, even though there are some portions of backup or restore datathat have been completed.

Apparently, the backup admin would need a backup application thatprovides a service-level agreement (SLA) of achieving any successivebackup or restore from an improper or random or unintended abort to becontinuous in nature. The aim of a backup admin during such scenarioswould be to have the successive backup or restore to be started from thepoint of abort, without the necessity of having to restart from thebeginning, and to avoid any further increase in the backup or restorewindow.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are illustrated by way of example and notlimitation in the figures of the accompanying drawings in which likereferences indicate similar elements.

FIG. 1 is a block diagram illustrating a storage system according to oneembodiment.

FIGS. 2A-2F are block diagrams illustrating a backup operation accordingto one embodiment.

FIGS. 3A-3F are block diagrams illustrating a restore operationaccording to one embodiment.

FIG. 4 is a flow diagram illustrating a method for backing up data to atarget device according to one embodiment.

FIG. 5 is a flow diagram illustrating a method for restoring data from atarget device according to one embodiment.

FIG. 6 is a block diagram illustrating a data processing systemaccording to one embodiment.

DETAILED DESCRIPTION

Various embodiments and aspects of the inventions will be described withreference to details discussed below, and the accompanying drawings willillustrate the various embodiments. The following description anddrawings are illustrative of the invention and are not to be construedas limiting the invention. Numerous specific details are described toprovide a thorough understanding of various embodiments of the presentinvention. However, in certain instances, well-known or conventionaldetails are not described in order to provide a concise discussion ofembodiments of the present inventions.

Reference in the specification to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin conjunction with the embodiment can be included in at least oneembodiment of the invention. The appearances of the phrase “in oneembodiment” in various places in the specification do not necessarilyall refer to the same embodiment.

Embodiments of the invention disclose how the data probe approach hasbeen used to identify the abrupt abort during a backup operation, andensure a safe uninterrupted backup from the aborted point in the nextbackup session. In one embodiment, a cache disk array is used to holdmarginal footprints of the data to be write-latched for the backupoperation at any instance of time. Backup agent may utilize thesefootprints after an aborted backup to understand the current set of datapackets that has to be consumed for the immediate write operationresulting in an uninterrupted backup session.

Embodiments of the invention further disclose a solution to avoid anincrease in the backup window due to an unexpected abort. The solutionensures an uninterrupted backup service after an unintended terminationof the backup session.

Embodiments of the invention further disclose how the data probeapproach has been used to identify the abrupt abort during a restoreoperation and ensure a safe uninterrupted restore from the aborted pointin the next restore session. In one embodiment, a cache disk array isused to hold marginal footprints of the data to be constructed for therestore operation at any instant of time. Restore agent may utilizethese footprints after an aborted restore to understand the current setof data packets that has to be consumed for the immediate read operationresulting in an uninterrupted restore session.

Embodiments of the invention further disclose a solution to avoid anincrease in the restore window due to an unexpected abort. The solutionalso ensures an uninterrupted restore service after an unintendedtermination of the restore session to prevent a corrupted productiondata.

According to some embodiments, a method for backing up data to a targetdevice is described. The method receives a first set of data packets forbackup, where the first set of data packets includes a multiplicity ofdata chunks. The method further captures footprints of the first set ofdata packets in a cache disk array. In response to receiving anacknowledgement from the cache disk array indicating the footprints havebeen captured, the method further initiates a write operation to writeeach data chunk of the first set of data packets to the target device.In response to receiving an acknowledgement indicating the data chunk issuccessfully written, the method further flushes the respectivefootprint of the data chunk from the cache disk array.

According to another embodiment, a method for restoring data from atarget device is described. The method receives a first set of datapackets for restore, where the first set of data packets includes amultiplicity of data chunks. The method further captures footprints ofthe first set of data packets in a cache disk array. In response toreceiving an acknowledgement from the cache disk array indicating thefootprints of the first set of data packets have been captured, themethod pushes each data chunk of the first set of data packets to aconstruction container for reconstruction of backup data. In response toreceiving an acknowledgement from the construction container indicatingthe data chunk is successfully pushed, the method flushes the respectivefootprint of the data chunk from the cache disk array.

FIG. 1 is a block diagram illustrating a storage system according to oneembodiment of the invention. Referring to FIG. 1, system 100 includes,but is not limited to, one or more client systems 101-102communicatively coupled to storage system 104 over network 103. Clients101-102 may be any type of clients such as a host or server, a personalcomputer (e.g., desktops, laptops, and tablets), a “thin” client, apersonal digital assistant (PDA), a Web enabled appliance, or a mobilephone (e.g., Smartphone), etc. Alternatively, any of clients 101-102 maybe a primary storage system (e.g., local data center) that providesstorage to other local clients, which may periodically back up thecontent stored therein to a backup storage system (e.g., a disasterrecovery site or system), such as storage system 104. Network 103 may beany type of networks such as a local area network (LAN), a wide areanetwork (WAN) such as the Internet, a fiber network, a storage network,or a combination thereof, wired or wireless. Clients 101-102 may be inphysical proximity or may be physically remote from one another. Storagesystem 104 may be located in proximity to one, both, or neither ofclients 101-102.

Storage system 104 may include or represent any type of servers or acluster of one or more servers (e.g., cloud servers). For example,storage system 104 may be a storage server used for various differentpurposes, such as to provide multiple users or client systems withaccess to shared data and/or to back up (or restore) data (e.g., missioncritical data). Storage system 104 may provide storage services toclients or users via a variety of access interfaces and/or protocolssuch as file-based access protocols and block-based access protocols.The file-based access protocols may include the network file system(NFS) protocol, common Internet file system (CIFS) protocol, and directaccess file system protocol, etc. The block-based access protocols mayinclude the small computer system interface (SCSI) protocols, InternetSCSI or iSCSI, and Fibre channel (FC) protocol, etc. Storage system 104may further provide storage services via an object-based protocol andHadoop distributed file system (HDFS) protocol.

In one embodiment, storage system 104 includes, but is not limited to,storage service engine 106 (also referred to as service logic, servicemodule, or service unit, which may be implemented in software, hardware,or a combination thereof), optional deduplication logic 107, and one ormore storage units or devices 108-109 communicatively coupled to eachother. Storage service engine 106 may represent any storage servicerelated components configured or adapted to provide storage services(e.g., storage as a service) to a variety of clients using any of theaccess protocols set forth above. For example, storage service engine106 may include backup logic 121 and restore logic 122. Backup logic oragent 121 is configured to receive and back up data from a client (e.g.,clients 101-102) and to store the backup data in any one or more ofstorage units 108-109. In one embodiment, the backup data may be loadedinto write latch 125, and write latch 125 is configured to write thebackup data to a target device (e.g., storage units 108-109). Restorelogic or agent 122 is configured to retrieve and restore backup datafrom any one or more of storage units 108-109 back to a client (e.g.,clients 101-102). In one embodiment, to restore the backup data, readlatch 126 may read the data from a target device (e.g., storage units108-109), where the data is loaded into read latch 126. In oneembodiment, cache disk array 151 is an emulated disk array carved outfrom a source under backup and/or restore host. In FIG. 1, cache diskarray 151 is installed on each of client 101-102, though cache diskarray 151 may be installed on storage system 104. In one embodiment,cache disk array 151 may temporarily store marginal footprints of thebackup data. Construction container 127 (e.g., conditional constructioncontainer) may receive restore backup data from restore agent 122 andconstruct the received backup data until the reconstruction iscompleted.

Storage units 108-109 may be implemented locally (e.g., single nodeoperating environment) or remotely (e.g., multi-node operatingenvironment) via interconnect 120, which may be a bus and/or a network(e.g., a storage network or a network similar to network 103). Storageunits 108-109 may include a single storage device such as a hard disk, atape drive, a semiconductor memory, multiple storage devices such as aredundant array system (e.g., a redundant array of independent disks(RAID)), a system for storage such as a library system or networkattached storage system, or any other appropriate storage device orsystem. Some of storage units 108-109 may be located locally or remotelyaccessible over a network.

In response to a data file to be stored in storage units 108-109,according to one embodiment, deduplication logic 107 is configured tosegment the data file into multiple segments (also referred to aschunks), for example as data objects 112-113, according to a variety ofsegmentation policies or rules. Deduplication logic 107 may choose notto store a segment in a storage unit if the segment has been previouslystored in the storage unit. In the event that deduplication logic 107chooses not to store the segment in the storage unit, it stores metadataenabling the reconstruction of the file using the previously storedsegment. As a result, segments of data files are stored in adeduplicated manner, either within each of storage units 108-109 oracross at least some of storage units 108-109. The metadata, such asmetadata 110-111, may be stored in at least some of storage units108-109, such that files can be accessed independent of another storageunit. Metadata of each storage unit includes enough information toprovide access to the files it contains.

FIGS. 2A-2F are block diagrams illustrating a backup operation accordingto one embodiment. Referring to FIGS. 2A-2F, backup agent 121 receives aset of data packets (referred to as “Data Set 1” in FIG. 2A) that needsto be write-latched for the write operation. In addition, marginalfootprints associated with the set of data packets may be stored incache disk array 151. As previously described, a cache disk array refersto an emulated disk array that is carved out from the source underbackup. For example, if there are two servers that are being backed up,the cache availability may be noted and emulated for a generic cachedisk array and utilized by the backup agent 121. The followingchronology illustrates the solution step by step:

Referring to FIG. 2A, the first set of data packets (“Data Set 1”) arereceived by backup agent 121. The marginal footprints of the first setof data packets are captured in cache disk array 151. The marginalfootprints may include minimal data properties, such as last byteinformation, logical address on the storage, sector information, packetmetadata information, etc. Concurrently, write latch 125 may beindicated by the backup agent 121 with a ‘wait’ signal to initiate thewrite operation.

Referring to FIG. 2B, the cache disk array (CDA) 151 acknowledges (e.g.,“ACK” signal) the capture of the footprints of Data Set 1 to the backupagent 121. Consequently, the backup agent 121 initiates a writeoperation to write latch 125 and loads Data Set 1 into write latch 125.At the same time, a second set of data packets (“Data Set 2”) may be ona ‘hold’ state at backup agent 121.

Referring to FIG. 2C, data chunks (e.g., byte-by-byte) from Data Set 1is written successfully to a target device and acknowledged by writelatch 125 to the backup agent 121. Subsequently, backup agent 121 mayflush the respective footprint of each data chunk from CDA 151. This isto ensure that there is a regular track on the data chunks (e.g., bytes)transferred successfully to the target device. Once the data chunks aresuccessfully written to the target device, the footprints from CDA 151may be flushed by backup agent 121 to ensure the space for the next setof footprints.

Referring to FIG. 2D, if the write operation is aborted, for example inresponse to an unexpected signal, backup agent 121 may freeze the CDA151 (e.g., by communicating a ‘FREEZE’ signal) at the point in timewhere the last data chunk (e.g., last byte) was successfully written. Inthis way, the CDA 151 may be used as reference for the last data chunkthat has been successfully transferred to the target device.Concurrently, the write latch 125 may be terminated and result in thefinal backup termination.

Referring to FIG. 2E, when the next backup is triggered, CDA 151 mayinitially be queried for the captured footprints (or remainingfootprints as some may have been flushed), and the last data chunk thatwas transferred from the data set (e.g., Data Set 1) may be identifiedbased on the footprints. From the marginal footprints captured in CDA151, all of the information regarding the last data set that wastransferred may be retrieved by the backup agent 121. The backup agent121 may now retrieve the data set or data chunk that was to-be-writtenfrom the point in time where it was aborted. Accordingly, a start signalto the write latch 125 may be provided, and an ‘Unfreeze’ signal may becommunicated to the CDA 151 to start the data tracking.

Referring to FIG. 2F, once the backup is completed, the next data setmay be retrieved by the backup agent 121 with a ‘release’ signal to theagent input.

FIGS. 3A-3F are block diagrams illustrating a restore operationaccording to one embodiment. Referring to FIGS. 3A-3F, restore agent 122receives a set of data packets (referred to as “Data Set 1” in FIG. 3A)that is read-latched for the reconstruction and storing of the marginalfootprints in cache disk array 151. Here, cache disk array 151 may bereferred to as an emulated disk array that is carved out from therestore host. Also, the restore agent 122 ensures that the set of datapackets being read from target device 310 (e.g., storage units 108-109of FIG. 1) may be routed to a construction container 127 (e.g.,conditional construction container (CCC)) in order to make sure that thereplay happens only after the last data chunk (e.g., last byte of data)has been successfully read from the target device. Following chronologyillustrates the solution step by step:

Referring to FIG. 3A, a first set of data packets (Data Set 1) isreceived by the restore agent 122 from read latch 126. For example,restore agent 122 may communicate a ‘release’ signal to read latch 126.In turn, read latch 126 may communicate a ‘request’ signal to targetdevice 310 to receive or retrieve the first set of data packets andprovide the first set of data packets to restore agent 122. Marginalfootprints of the first set of data packets are captured in cache diskarray 151. Marginal footprints may include minimal data properties, suchas last byte information, logical address on the storage, sectorinformation, packet metadata information, etc. Concurrently, the readlatch 126 may be indicated by restore agent 122 with a ‘wait’ signal toinitiate a successive read operation. Container 127 may also receive a‘wait’ signal from restore agent 122.

Referring to FIG. 3B, cache disk array 151 acknowledges the capture ofthe footprints of Data Set 1 to the restore agent 122. Consequently, therestore agent 122 initiates a ‘PUSH’ signal to container 127 to pushData Set 1 to container 127. At the same time, a second set of datapackets is on a ‘hold’ state at the read latch 126 (as indicated byrestore agent 122).

Referring to FIG. 3C, data chunks from Data Set 1 (e.g., byte-by-byte)are pushed successfully to container 127 and the pushed data chunks areacknowledged by the container 127. Consequently, the restore agent 122may flush the respective footprint of each data chunk from cache diskarray 151. This is to ensure that there is a regular track on the datachunks (e.g., bytes) pushed successfully to container 127. Once the datachunks are successfully pushed to container 127, the footprints fromcache disk array 151 may be flushed by restore agent 122 to ensure thespace for the next set of footprints.

Referring to FIG. 3D, if the read operation is aborted with anunexpected signal, the restore agent 122 may ‘freeze’ the cache diskarray 151 at the point in time where the last data chunk (e.g., the lastbyte) was pushed successfully. In this way, cache disk array 151 is usedas a reference for the last data chunk that has been successfully readand pushed to container 127. Concurrently, the read operation may beterminated and results in a final restore termination.

Referring to FIG. 3E, when the next restore is triggered, cache diskarray 151 may initially be queried for the captured footprints (orremaining footprints as some of the captured footprints may have beenflushed), and the last data chunk that was successfully pushed tocontainer 127 may be identified based on the footprints. From themarginal footprints captured in cache disk array 151, all of theinformation regarding the last data set that was read may be retrievedby the restore agent 122. Also, the restore agent 122 may perform ahealth check of the container data in container 127 to ensure theavailable data is healthy and sufficient to reconstruct. If the recentdata chunks (e.g., bytes) during the abort are not healthy to bereconstructed, then the read latch 126 may be indicated or commanded tore-query those data chunks as the starting point. Otherwise, the lastdata chunk information (e.g., footprints) from cache disk array 151 maybe used to restart the restore as an uninterrupted one. The restoreagent 122 may now retrieve the data set that was to be read from thepoint where it was aborted. Accordingly, a start or ‘release’ signal tothe read latch 126 may be provided. An ‘unfreeze’ signal may also becommunicated to cache disk array 151 to start the data tracking.

Referring to FIG. 3F, once the restore is completed, then the next dataset may be retrieved by restore agent 122 with a ‘release’ signal toread latch 126.

FIG. 4 is a flow diagram illustrating a method for backing up data to atarget device according to one embodiment. Process 400 may be performedby processing logic that includes hardware (e.g. circuitry, dedicatedlogic, etc.), software (e.g., embodied on a non-transitory computerreadable medium), or a combination thereof. For example, process 400 maybe performed by backup agent 121 and/or write latch 125 of FIG. 1.

Referring to FIG. 4, at block 410, the processing logic receives a firstset of data packets for backup, where the first set of data packetsincludes a multiplicity of data chunks. At block 420, the processinglogic captures footprints of the first set of data packets in a cachedisk array (e.g., cache disk array 151 of FIG. 1). At block 430, inresponse to receiving an acknowledgement from the cache disk arrayindicating the footprints have been captured, the processing logicinitiates a write operation to write each data chunk of the first set ofdata packets to a target device (e.g., storage units 108-109). At block440, in response to receiving an acknowledgement indicating the datachunk is successfully written, the processing logic flushes therespective footprint of the data chunk from the cache disk array.

FIG. 5 is a flow diagram illustrating a method for restoring data from atarget device according to one embodiment. Process 500 may be performedby processing logic that includes hardware (e.g. circuitry, dedicatedlogic, etc.), software (e.g., embodied on a non-transitory computerreadable medium), or a combination thereof. For example, process 500 maybe performed by restore agent 122, read latch 126, and/or constructioncontainer 127 of FIG. 1.

Referring to FIG. 5, at block 510, the processing logic receives a firstset of data packets for restore, where the first set of data packetsincludes a multiplicity of data chunks. At block 520, the processinglogic captures footprints of the first set of data packets in a cachedisk array. At block 530, in response to receiving an acknowledgementfrom the cache disk array indicating the footprints of the first set ofdata packets have been captured, the processing logic pushes each datachunk of the first set of data packets to a construction container forreconstruction of backup data. At block 540, in response to receiving anacknowledgement from the construction container indicating the datachunk is successfully pushed, the processing logic flushes therespective footprint of the data chunk from the cache disk array.

Note that some or all of the components as shown and described above(e.g., backup agent 121, restore agent 122, write latch 125, read latch126, construction container 127 of FIG. 1) may be implemented insoftware, hardware, or a combination thereof. For example, suchcomponents can be implemented as software installed and stored in apersistent storage device, which can be loaded and executed in a memoryby a processor (not shown) to carry out the processes or operationsdescribed throughout this application. Alternatively, such componentscan be implemented as executable code programmed or embedded intodedicated hardware such as an integrated circuit (e.g., an applicationspecific IC or ASIC), a digital signal processor (DSP), or a fieldprogrammable gate array (FPGA), which can be accessed via acorresponding driver and/or operating system from an application.Furthermore, such components can be implemented as specific hardwarelogic in a processor or processor core as part of an instruction setaccessible by a software component via one or more specificinstructions.

FIG. 6 is a block diagram illustrating an example of a data processingsystem which may be used with one embodiment. For example, system 1500may represents any of data processing systems described above performingany of the processes or methods described above. System 1500 can includemany different components. These components can be implemented asintegrated circuits (ICs), portions thereof, discrete electronicdevices, or other modules adapted to a circuit board such as amotherboard or add-in card of the computer system, or as componentsotherwise incorporated within a chassis of the computer system. Notealso that system 1500 is intended to show a high level view of manycomponents of the computer system. However, it is to be understood thatadditional components may be present in certain implementations andfurthermore, different arrangement of the components shown may occur inother implementations. System 1500 may represent a desktop, a laptop, atablet, a server, a mobile phone, a media player, a personal digitalassistant (PDA), a personal communicator, a gaming device, a networkrouter or hub, a wireless access point (AP) or repeater, a set-top box,or a combination thereof. Further, while only a single machine or systemis illustrated, the term “machine” or “system” shall also be taken toinclude any collection of machines or systems that individually orjointly execute a set (or multiple sets) of instructions to perform anyone or more of the methodologies discussed herein.

In one embodiment, system 1500 includes processor 1501, memory 1503, anddevices 1505-1508 via a bus or an interconnect 1510. Processor 1501 mayrepresent a single processor or multiple processors with a singleprocessor core or multiple processor cores included therein. Processor1501 may represent one or more general-purpose processors such as amicroprocessor, a central processing unit (CPU), or the like. Moreparticularly, processor 1501 may be a complex instruction set computing(CISC) microprocessor, reduced instruction set computing (RISC)microprocessor, very long instruction word (VLIW) microprocessor, orprocessor implementing other instruction sets, or processorsimplementing a combination of instruction sets. Processor 1501 may alsobe one or more special-purpose processors such as an applicationspecific integrated circuit (ASIC), a cellular or baseband processor, afield programmable gate array (FPGA), a digital signal processor (DSP),a network processor, a graphics processor, a network processor, acommunications processor, a cryptographic processor, a co-processor, anembedded processor, or any other type of logic capable of processinginstructions.

Processor 1501, which may be a low power multi-core processor socketsuch as an ultra-low voltage processor, may act as a main processingunit and central hub for communication with the various components ofthe system. Such processor can be implemented as a system on chip (SoC).Processor 1501 is configured to execute instructions for performing theoperations and steps discussed herein. System 1500 may further include agraphics interface that communicates with optional graphics subsystem1504, which may include a display controller, a graphics processor,and/or a display device.

Processor 1501 may communicate with memory 1503, which in one embodimentcan be implemented via multiple memory devices to provide for a givenamount of system memory. Memory 1503 may include one or more volatilestorage (or memory) devices such as random access memory (RAM), dynamicRAM (DRAM), synchronous DRAM (SDRAM), static RAM (SRAM), or other typesof storage devices. Memory 1503 may store information includingsequences of instructions that are executed by processor 1501, or anyother device. For example, executable code and/or data of a variety ofoperating systems, device drivers, firmware (e.g., input output basicsystem or BIOS), and/or applications can be loaded in memory 1503 andexecuted by processor 1501. An operating system can be any kind ofoperating systems, such as, for example, Windows operating system fromMicrosoft®, Mac OS®/iOS® from Apple, Android® from Google®, Linux®,Unix®, or other real-time or embedded operating systems such as VxWorks.

System 1500 may further include IO devices such as devices 1505-1508,including network interface device(s) 1505, optional input device(s)1506, and other optional 10 device(s) 1507. Network interface device1505 may include a wireless transceiver and/or a network interface card(NIC). The wireless transceiver may be a WiFi transceiver, an infraredtransceiver, a Bluetooth transceiver, a WiMax transceiver, a wirelesscellular telephony transceiver, a satellite transceiver (e.g., a globalpositioning system (GPS) transceiver), or other radio frequency (RF)transceivers, or a combination thereof. The NIC may be an Ethernet card.

Input device(s) 1506 may include a mouse, a touch pad, a touch sensitivescreen (which may be integrated with display device 1504), a pointerdevice such as a stylus, and/or a keyboard (e.g., physical keyboard or avirtual keyboard displayed as part of a touch sensitive screen). Forexample, input device 1506 may include a touch screen controller coupledto a touch screen. The touch screen and touch screen controller can, forexample, detect contact and movement or break thereof using any of aplurality of touch sensitivity technologies, including but not limitedto capacitive, resistive, infrared, and surface acoustic wavetechnologies, as well as other proximity sensor arrays or other elementsfor determining one or more points of contact with the touch screen.

IO devices 1507 may include an audio device. An audio device may includea speaker and/or a microphone to facilitate voice-enabled functions,such as voice recognition, voice replication, digital recording, and/ortelephony functions. Other IO devices 1507 may further include universalserial bus (USB) port(s), parallel port(s), serial port(s), a printer, anetwork interface, a bus bridge (e.g., a PCI-PCI bridge), sensor(s)(e.g., a motion sensor such as an accelerometer, gyroscope, amagnetometer, a light sensor, compass, a proximity sensor, etc.), or acombination thereof. Devices 1507 may further include an imagingprocessing subsystem (e.g., a camera), which may include an opticalsensor, such as a charged coupled device (CCD) or a complementarymetal-oxide semiconductor (CMOS) optical sensor, utilized to facilitatecamera functions, such as recording photographs and video clips. Certainsensors may be coupled to interconnect 1510 via a sensor hub (notshown), while other devices such as a keyboard or thermal sensor may becontrolled by an embedded controller (not shown), dependent upon thespecific configuration or design of system 1500.

To provide for persistent storage of information such as data,applications, one or more operating systems and so forth, a mass storage(not shown) may also couple to processor 1501. In various embodiments,to enable a thinner and lighter system design as well as to improvesystem responsiveness, this mass storage may be implemented via a solidstate device (SSD). However in other embodiments, the mass storage mayprimarily be implemented using a hard disk drive (HDD) with a smalleramount of SSD storage to act as a SSD cache to enable non-volatilestorage of context state and other such information during power downevents so that a fast power up can occur on re-initiation of systemactivities. Also a flash device may be coupled to processor 1501, e.g.,via a serial peripheral interface (SPI). This flash device may providefor non-volatile storage of system software, including a basicinput/output software (BIOS) as well as other firmware of the system.

Storage device 1508 may include computer-accessible storage medium 1509(also known as a machine-readable storage medium or a computer-readablemedium) on which is stored one or more sets of instructions or software(e.g., processing module, unit, and/or logic 1528) embodying any one ormore of the methodologies or functions described herein. Processingmodule/unit/logic 1528 may represent any of the components describedabove, such as, for example, modules 121-127 as described above.Processing module/unit/logic 1528 may also reside, completely or atleast partially, within memory 1503 and/or within processor 1501 duringexecution thereof by data processing system 1500, memory 1503 andprocessor 1501 also constituting machine-accessible storage media.Processing module/unit/logic 1528 may further be transmitted or receivedover a network via network interface device 1505.

Computer-readable storage medium 1509 may also be used to store the somesoftware functionalities described above persistently. Whilecomputer-readable storage medium 1509 is shown in an exemplaryembodiment to be a single medium, the term “computer-readable storagemedium” should be taken to include a single medium or multiple media(e.g., a centralized or distributed database, and/or associated cachesand servers) that store the one or more sets of instructions. The terms“computer-readable storage medium” shall also be taken to include anymedium that is capable of storing or encoding a set of instructions forexecution by the machine and that cause the machine to perform any oneor more of the methodologies of the present invention. The term“computer-readable storage medium” shall accordingly be taken toinclude, but not be limited to, solid-state memories, and optical andmagnetic media, or any other non-transitory machine-readable medium.

Processing module/unit/logic 1528, components and other featuresdescribed herein can be implemented as discrete hardware components orintegrated in the functionality of hardware components such as ASICS,FPGAs, DSPs or similar devices. In addition, processingmodule/unit/logic 1528 can be implemented as firmware or functionalcircuitry within hardware devices. Further, processing module/unit/logic1528 can be implemented in any combination hardware devices and softwarecomponents.

Note that while system 1500 is illustrated with various components of adata processing system, it is not intended to represent any particulararchitecture or manner of interconnecting the components; as suchdetails are not germane to embodiments of the present invention. It willalso be appreciated that network computers, handheld computers, mobilephones, servers, and/or other data processing systems which have fewercomponents or perhaps more components may also be used with embodimentsof the invention.

Some portions of the preceding detailed descriptions have been presentedin terms of algorithms and symbolic representations of operations ondata bits within a computer memory. These algorithmic descriptions andrepresentations are the ways used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here, and generally,conceived to be a self-consistent sequence of operations leading to adesired result. The operations are those requiring physicalmanipulations of physical quantities.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the above discussion, itis appreciated that throughout the description, discussions utilizingterms such as those set forth in the claims below, refer to the actionand processes of a computer system, or similar electronic computingdevice, that manipulates and transforms data represented as physical(electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission or display devices.

Embodiments of the invention also relate to an apparatus for performingthe operations herein. Such a computer program is stored in anon-transitory computer readable medium. A machine-readable mediumincludes any mechanism for storing information in a form readable by amachine (e.g., a computer). For example, a machine-readable (e.g.,computer-readable) medium includes a machine (e.g., a computer) readablestorage medium (e.g., read only memory (“ROM”), random access memory(“RAM”), magnetic disk storage media, optical storage media, flashmemory devices).

The processes or methods depicted in the preceding figures may beperformed by processing logic that comprises hardware (e.g. circuitry,dedicated logic, etc.), software (e.g., embodied on a non-transitorycomputer readable medium), or a combination of both. Although theprocesses or methods are described above in terms of some sequentialoperations, it should be appreciated that some of the operationsdescribed may be performed in a different order. Moreover, someoperations may be performed in parallel rather than sequentially.

Embodiments of the present invention are not described with reference toany particular programming language. It will be appreciated that avariety of programming languages may be used to implement the teachingsof embodiments of the invention as described herein.

In the foregoing specification, embodiments of the invention have beendescribed with reference to specific exemplary embodiments thereof. Itwill be evident that various modifications may be made thereto withoutdeparting from the broader spirit and scope of the invention as setforth in the following claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

1. A computer-implemented method for restoring data from a target device onto a source device by a restore agent, comprising: using cache availability on the source device to emulate a cache disk array to be utilized by the restore agent; receiving a first set of data packets for restore, wherein the first set of data packets comprises a plurality of data chunks; capturing footprints of the first set of data packets in the cache disk array; in response to receiving an acknowledgement from the cache disk array indicating the footprints of the first set of data packets have been captured, pushing each data chunk of the first set of data packets to a construction container for reconstruction of backup data, in response to receiving an acknowledgement from the construction container indicating the data chunk is successfully pushed, flushing the footprint of the data chunk from the cache disk array, and in response to receiving an unexpected abort signal indicating a read operation is aborted, sending a freeze signal from the restore agent to the cache disk array thereby freezing the cache disk array at a point in time where a last data chunk was successfully pushed to the construction container.
 2. (canceled)
 3. The method of claim 21, further comprising: in response to receiving a trigger for a next restore, querying remaining footprints of the first set of data packets from the cache disk array, and identifying the last data chunk that was successfully pushed to the construction container based on the queried footprints.
 4. The method of claim 3, further comprising: in response to receiving a trigger for a next restore, performing a health check of container data in the construction container, if recent data chunks from the container data are insufficient to be reconstructed, re-querying the recent data chunks from the target device as a starting point for the next restore, otherwise if the recent data chunks are sufficient to reconstruct, using the identified last data chunk as the starting point.
 5. The method of claim 4, further comprising: unfreezing the cache disk array.
 6. The method of claim 1, further comprising: when the restore is completed, receiving a second set of data packets for restore, and capturing footprints of the second set of data packets in the cache disk array.
 7. The method of claim 1, wherein the footprints of the first set of data packets include last byte information, logical address on a storage, sector information, and packet metadata information.
 8. The method of claim 1, further comprising: indicating a read latch to hold a second set of data packets at the read latch.
 9. A non-transitory machine-readable medium having instructions stored therein, which when executed by a processor, cause the processor to perform operations for, the operations comprising: using restore agent to determine cache availability on a source device and emulating a cache disk array on the source device to be utilized by the restore agent; receiving a first set of data packets for restore, wherein the first set of data packets comprises a plurality of data chunks; capturing footprints of the first set of data packets in the cache disk array; in response to receiving an acknowledgement from the cache disk array indicating the footprints of the first set of data packets have been captured, pushing each data chunk of the first set of data packets to a construction container for reconstruction of backup data, in response to receiving an acknowledgement from the construction container indicating the data chunk is successfully pushed, flushing the footprint of the data chunk from the cache disk array, and in response to receiving an unexpected abort signal indicating a read operation is aborted, sending a freeze signal from the restore agent to the cache disk array thereby freezing the cache disk array at a point in time where a last data chunk was successfully pushed to the construction container.
 10. (canceled)
 11. The non-transitory machine-readable medium of claim 9, wherein the operations further comprise: in response to receiving a trigger for a next restore, querying remaining footprints of the first set of data packets from the cache disk array, and identifying the last data chunk that was successfully pushed to the construction container based on the queried footprints.
 12. The non-transitory machine-readable medium of claim 11, wherein the operations further comprise: in response to receiving a trigger for a next restore, performing a health check of container data in the construction container, if recent data chunks from the container data are insufficient to be reconstructed, re-querying the recent data chunks from the target device as a starting point for the next restore, otherwise if the recent data chunks are sufficient to reconstruct, using the identified last data chunk as the starting point.
 13. The non-transitory machine-readable medium of claim 12, wherein the operations further comprise: unfreezing the cache disk array.
 14. The non-transitory machine-readable medium of claim 9, wherein the operations further comprise: when the restore is completed, receiving a second set of data packets for restore, and capturing footprints of the second set of data packets in the cache disk array.
 15. The non-transitory machine-readable medium of claim 9, wherein the footprints of the first set of data packets include last byte information, logical address on a storage, sector information, and packet metadata information.
 16. The non-transitory machine-readable medium of claim 9, wherein the operations further comprise: indicating a read latch to hold a second set of data packets at the read latch.
 17. A data processing system, comprising: a processor; and a memory coupled to the processor to store instructions, which when executed by the processor, cause the processor to perform operations, the operations comprising: executing a restore agent on a storage system; using the restore agent to determine cache availability on a source device and emulating a cache disk array on the source device to be utilized by the restore agent; receiving a first set of data packets for restore, wherein the first set of data packets comprises a plurality of data chunks; capturing footprints of the first set of data packets in the cache disk array; in response to receiving an acknowledgement from the cache disk array indicating the footprints of the first set of data packets have been captured, pushing each data chunk of the first set of data packets to a construction container for reconstruction of backup data, in response to receiving an acknowledgement from the construction container indicating the data chunk is successfully pushed, flushing the footprint of the data chunk from the cache disk array in response to receiving an unexpected abort signal indicating a read operation is aborted, sending a freeze signal from the restore agent to the cache disk array thereby freezing the cache disk array at a point in time where a last data chunk was successfully pushed to the construction container.
 18. (canceled)
 19. The data processing system of claim 17, wherein the operations further comprise: in response to receiving a trigger for a next restore, querying remaining footprints of the first set of data packets from the cache disk array, and identifying the last data chunk that was successfully pushed to the construction container based on the queried footprints.
 20. The data processing system of claim 19, wherein the operations further comprise: in response to receiving a trigger for a next restore, performing a health check of container data in the construction container, if recent data chunks from the container data are insufficient to be reconstructed, re-querying the recent data chunks from the target device as a starting point for the next restore, otherwise if the recent data chunks are sufficient to reconstruct, using the identified last data chunk as the starting point.
 21. The data processing system of claim 20, wherein the operations further comprise: unfreezing the cache disk array.
 22. The data processing system of claim 17, wherein the operations further comprise: when the restore is completed, receiving a second set of data packets for restore, and capturing footprints of the second set of data packets in the cache disk array.
 23. The data processing system of claim 17, wherein the footprints of the first set of data packets include last byte information, logical address on a storage, sector information, and packet metadata information.
 24. The data processing system of claim 17, wherein the operations further comprise: indicating a read latch to hold a second set of data packets at the read latch. 